Late Transition Metal Catalyzed Chelation-Assisted C-H Alkynylation Reactions

In this thesis, we report the development of synthetic methods using late-transition metals as catalysts for the direct C−H alkynylation of functionalized molecules. The catalytic system we developed is based on ruthenium or rhodium catalysts, and converts C(sp²)−H bonds into C(sp²)−alkyne bonds using a broad range of widely used functional groups as chelating group. These chelating groups are phenolic -OH, carboxylic acid, ester, ketone, ether, amine, thioether, sulfoxide, sulfone, phenol ester, carbamate, aldehyde and nitro groups. We next applied these reactions in the synthesis of polyaromatic hydrocarbons (PAH) such as extended fluoranthenes and dibenzopentalenes. The mechanisms of these reactions were studied both experimentally and computationally, showing that the efficiency of these catalytic systems arises from two low-barrier steps: bromo-alkyne insertion into a ruthena- or rhoda-cycle, followed by bromide elimination. In the case of nitrobenzenes, we also observed an electrophilic C−H rhodation process.

Finally, we extended this catalytic system to the alkynylation of C(sp³)−H bonds using an iridium catalyst and oxime ethers or nitrogen heterocycles as directing groups.